Two weeks ago the race was essentially even, with Mr McCain at 49% and Mr Obama at 47%, the Post reported.

Mr Obama claimed a lead in the polls after emerging victorious from a bitterly-fought primary contest against Hillary Clinton, who had started as the overwhelming favourite to front their party’s White House bid.

The Democrats’ attempt to depict Mr McCain as representing four more years of George W Bush resonated with many Americans who are deeply unhappy with the present President.